Detailed Description
The QDragObject class encapsulates MIME-based data
transfer.
QDragObject is the base class for all data that needs to be
transferred between and within applications, both for drag and
drop and for the clipboard.
See the Drag-and-drop documentation for an
overview of how to provide drag and drop in your application.
See the QClipboard documentation for an overview of how to provide
cut-and-paste in your application.
The drag() function is used to start a drag operation. You can
specify the DragMode in the call or use one of the convenience
functions dragCopy(), dragMove() or dragLink(). The drag source
where the data originated is retrieved with source(). If the data
was dropped on a widget within the application, target() will
return a pointer to that widget. Specify the pixmap to display
during the drag with setPixmap().
See also Drag And Drop Classes.
Member Type Documentation
QDragObject::DragMode
This enum describes the possible drag modes.
- QDragObject::DragDefault - The mode is determined heuristically.
- QDragObject::DragCopy - The data is copied, never moved.
- QDragObject::DragMove - The data is moved, if dragged at all.
- QDragObject::DragLink - The data is linked, if dragged at all.
- QDragObject::DragCopyOrMove - The user chooses the mode by using a
control key to switch from the default.
Member Function Documentation
QDragObject::QDragObject ( QWidget * dragSource = 0, const char * name = 0 )
Constructs a drag object called name, which is a child of dragSource.
Note that the drag object will be deleted when dragSource is
deleted.
QDragObject::~QDragObject () [virtual]
Destroys the drag object, canceling any drag and drop operation in
which it is involved, and frees up the storage used.
bool QDragObject::drag ()
Starts a drag operation using the contents of this object, using
DragDefault mode.
The function returns TRUE if the caller should delete the original
copy of the dragged data (but see target()); otherwise returns
FALSE.
If the drag contains references to information (e.g. file names
in a QUriDrag are references) then the return value should always
be ignored, as the target is expected to manipulate the
referred-to content directly. On X11 the return value should
always be correct anyway, but on Windows this is not necessarily
the case (e.g. the file manager starts a background process to
move files, so the source must not delete the files!)
Note that on Windows the drag operation will spin a blocking modal
event loop that will not dispatch any QTimers.
Example: dirview/dirview.cpp.
bool QDragObject::drag ( DragMode mode ) [virtual protected]
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Starts a drag operation using the contents of this object.
At this point, the object becomes owned by Qt, not the
application. You should not delete the drag object or anything it
references. The actual transfer of data to the target application
will be done during future event processing - after that time the
drag object will be deleted.
Returns TRUE if the dragged data was dragged as a move,
indicating that the caller should remove the original source of
the data (the drag object must continue to have a copy); otherwise
returns FALSE.
The mode specifies the drag mode (see
QDragObject::DragMode.) Normally one of the simpler drag(),
dragMove(), or dragCopy() functions would be used instead.
void QDragObject::dragCopy ()
Starts a drag operation using the contents of this object, using
DragCopy mode. Be sure to read the constraints described in
drag().
See also drag(), dragMove(), and dragLink().
Example: iconview/simple_dd/main.cpp.
void QDragObject::dragLink ()
Starts a drag operation using the contents of this object, using
DragLink mode. Be sure to read the constraints described in
drag().
See also drag(), dragCopy(), and dragMove().
bool QDragObject::dragMove ()
Starts a drag operation using the contents of this object, using
DragMove mode. Be sure to read the constraints described in
drag().
See also drag(), dragCopy(), and dragLink().
QPixmap QDragObject::pixmap () const
Returns the currently set pixmap (which isNull() if none is set).
QPoint QDragObject::pixmapHotSpot () const
Returns the currently set pixmap hotspot.
void QDragObject::setPixmap ( QPixmap pm, const QPoint & hotspot ) [virtual]
Set the pixmap pm to display while dragging the object. The
platform-specific implementation will use this where it can - so
provide a small masked pixmap, and do not assume that the user
will actually see it. For example, cursors on Windows 95 are of
limited size.
The hotspot is the point on (or off) the pixmap that should be
under the cursor as it is dragged. It is relative to the top-left
pixel of the pixmap.
Warning: We have seen problems with drag cursors on different
graphics hardware and driver software on Windows. Setting the
graphics acceleration in the display settings down one tick solved
the problems in all cases.
Example: fileiconview/qfileiconview.cpp.
void QDragObject::setPixmap ( QPixmap pm ) [virtual]
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Uses a hotspot that positions the pixmap below and to the right of
the mouse pointer. This allows the user to clearly see the point
on the window which they are dragging the data onto.
QWidget * QDragObject::source ()
Returns a pointer to the drag source where this object originated.
QWidget * QDragObject::target () [static]
After the drag completes, this function will return the QWidget
which received the drop, or 0 if the data was dropped on another
application.
This can be useful for detecting the case where drag and drop is
to and from the same widget.
This file is part of the Qt toolkit.
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Trolltech. All Rights Reserved.
